3D pen



FIG. 1 is a front elevational view of a 3D pen showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof,

FIG. 4 is a right side elevational view thereof; and,

FIG. 5 is a front perspective view thereof.

The broken lines in the figures depict portions of the 3D pen that form no part of the claimed design. 

CLAIM The ornamental design for a 3D pen, as shown and described. 